The present invention relates to a thin film laser emitting device and a method for the manufacture thereof; and, more particularly, to a thin film laser emitting device and a method for the manufacture thereof, the laser emitting device incorporating therein a thin film laser layer, a Bragg reflector for resonating and reflecting the light from the laser generation layer to generate laser and a laser emitting member for radiating the laser.
Semiconductor laser devices may be classified into edge emitting laser devices and surface emitting laser devices. An edge emitting device is provided with two cleaved facets serving as end faces of an optical resonator. The facets are normally formed by etching and function as reflectors of the laser generated inside the laser cavity. Generally, it is preferable that one of the facets has 100% reflectance and the other have a reflectance close to 100%, e.g., 99%. The laser generated inside the cavity is extracted through the facet with the lower reflectance. A surface emitting laser device may be constructed by integrating a reflecting surface close to the laser emitting facet of the side emitting laser diode to thereby guide the laser toward the top surface of the laser device. In either case, a multilayer thin film coating is required on each facet to control the reflectivity thereof.
However, the multilayer thin film coating may not be properly performed on a wafer basis in which the facets of the laser cavity are formed by a wafer process, e.g., dry etching carried out on a wafer scale. The thin film coating performed on the wafer basis may result in degradation or non-uniformity in the thickness of coating layer being formed on the facets of the laser device because incident angles of coating materials to the facets may not be controlled to be identical. As a result, there frequently occur spatial deviation and the temporal change in the reflectance of the facets. Further, it is also difficult to prevent the coating layers from being formed on other regions than the facets.
On the other hand, if the multilayer thin film coating is performed on a device basis after dicing the wafer into discrete laser devices, manufacturing efficiency is severely deteriorated and the advantage of the full wafer process can not be fully exploited. Further, in case of the surface emitting laser device described above, slant incident coating is still necessary due to the presence of the reflecting surface for guiding the laser toward the top surface.
In order to solve the foregoing problems, there is disclosed in Japanese Patent Laid-Open Publication No. 98-190123 a laser emitting device including corrugated diffraction grating formed on end faces of a resonator for controlling the reflectance thereof. The corrugated diffraction grating is formed by etching using an etching mask having a pattern corresponding to the grating.
Since, however, the corrugated grating is formed by etching on the end surfaces of the resonator in such a laser emitting device, the process therefor becomes complicated, lowering the productivity and increasing the manufacturing cost.
It is, therefore, an object of the present invention to provide a less costly and highly efficient thin film laser emitting device and a method for the manufacture thereof.
In accordance with one aspect of the present invention, there is provided a thin film laser emitting device, comprising:
a Bragg reflector including a recess and one or more diffraction gratings provided around the recess;
a thin film laser layer formed in the recess, for generating lights, the lights being reflected by the diffraction gratings;
a pair of electrodes, provided in the recess to have the thin film laser layer therebetween; and
a laser emitting means, provided at a portion of the gratings, for emanating the reflected lights.
In accordance with another aspect of the present invention, there is provided a method for manufacturing a thin film laser layer emitting device, comprising the steps of:
forming a Bragg reflector including a recess and one or more diffraction gratings provided around the recess;
forming a first electrode in the recess;
forming a thin film laser layer on the first electrode; and
forming a second electrode on the thin film laser layer.